Re: [PATCH v5] fs: clear file privilege bits when mmap writing

[Al Viro]

On Thu, Dec 10, 2015 at 01:45:09PM -0800, Kees Cook wrote:
> > but generally you need ->f_lock.  And in situations where the bit can
> > go only off->on, check it lockless, skip the whole thing entirely if it's
> > already set and grab the spinlock otherwise.
> 
> And I can take f_lock safely under mmap_sem?

Are you asking whether it's safe to take a spinlock under an rwsem?
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